In the printing industry, a desired image is repeatedly printed on a continuous web or substrate such as paper. In a typical printing process, the continuous web is slit in the longitudinal direction (the direction of web movement) to produce a plurality of continuous ribbons. The ribbons are aligned one on top of the other, folded longitudinally, and then cut laterally to produce a plurality of multi-page, approximately page-length segments, each of which is termed a "signature". The term signature also encompasses a single printed sheet that has or has not been folded. Because more than one different signature can be printed at one time, it is often desirable to separate the different signatures by transporting successive signatures in different directions or paths.
One way to accomplish the sorting of a single stream of signatures is to use a diverter mechanism such as a diverter wedge to divert successive signatures to one of two paths. Once diverted, the signatures typically are transferred to a conveyor using rotating buckets (also known in the art as fans, fan wheels, paddle fans, or rotary flywheels).
A typical configuration includes two sets of rotating buckets assemblies, one set to deliver signatures traveling along a first path to a conveyor and the other set to deliver signatures traveling along the second path to a conveyor. Each set of bucket assemblies includes several buckets arranged at a spaced distance from one another along a common axis or shaft. Each bucket has multiple aligned blades which define pockets or slots for receiving signatures and transferring the signature to the conveyor.
It is desirable to increase the operating speed of a printing press in order to increase the printed product output. However, as the rotational speed of the buckets is increased, it is more difficult to ensure the reliable operation of the buckets and ensure that the signatures are not damaged. For example, signature quality problems that can occur at higher press speeds include ink offset, dog-eared edges, and defects to both the leading and trailing edges of the signatures. These and other defects can lead to paper jams in the folder, resulting in press downtime and expense.
One type of prior art folder includes two sets of diverting areas therefore four bucket assemblies are needed to transfer the four different signatures types to four conveyors. The housing of such a folder typically includes only two bucket shafts on which are mounted the four bucket assemblies. Each shaft extends across the length of the folder housing and has two bucket assemblies thereon, one bucket assembly positioned on one end and the other bucket assembly positioned on the other end. One drive arrangement causes the rotation of both of the bucket assemblies on that respective shaft. The drive arrangement typically includes a series of shafts and pulleys driven by the folder drive mechanism, which includes a line shaft driven by the press motor. The drive arrangement drives the bucket shafts at the same operating speed as the other driven components of the folder. Therefore, individual control of the rotation of the bucket assemblies is not possible.
It is desirable to be able to individually control the rotation and the relative position of each bucket assembly in the folder to better control the rotational position of each bucket to match the timing at which the signatures enter the buckets of the bucket assemblies.